Ideally, in a microscope having a pivoting stand, the optical axis of the imaging system and the pivoting axis of the stand should be arranged perpendicular to one another. However, during the pivoting process, image and focus shifts occur when the surface of the object being viewed is not located in the plane of the pivoting axis, or when the detail being viewed is not located at the point of intersection of the axes.
The prior art contains a plurality of operating microscopes which can be freely positioned by means of a special suspension mechanism above the object being microscoped. For example, DE 42 13 312 A1 discloses an operating microscope in which, based on the magnification adjustment, the focusing speed is adjusted to enable a focus adjustment, tilt adjustment or canting adjustment. In this case, the zoom motor adjustment serves as a setting signal for the focus and for the X- or Y-adjustment. From DE 697 16 018 T2 and U.S. Pat. No. 5,825,536, control mechanisms for operating microscopes having multipart articulated arms are known. Motors are activated to cause the multiple arm sections to execute predefined movements. A force/torque sensor is used to determine an operating force in the direction of multiple axes, to enable arm sections and joints to be actuated in support of operation. An angle sensor is used to detect the current angle of each joint, enabling the position and the movement profile of the microscope to be calculated therefrom.
US Patent Publication 2005/0117207 A1 discloses an operating microscope having a multipart articulated arm and a controlling mechanism which holds the focus region largely constant independent of arm movement. In this case as well, angle sensors are used to detect the positions of the joints in order to determine the position of the microscope.
JP-2001059599-A2 and JP-2010102344-A2 describe a pivot arm stand for digital microscopes, which comprises a pivot arm which is pivotable about a horizontal rotational axis. The pivot arm comprises an upper focusing unit, which can be moved vertically along a column for preliminary coarse adjustment and clamped in place by means of a hand wheel. Parallel with the aforementioned simple column guide, a support for a zoom element/objective combination can be more finely positioned for focusing. The aforementioned specifications relate to the vertical adjustment of the pivot arm, i.e. when the pivot arm is pivoted about the rotational axis, the focusing movements take place under the corresponding pivot angle. To avoid disruptive misalignment, the user must adjust three knobs until the optical axis intersects with the actual rotational axis in question. For users who are inexperienced with such adjustment processes, it is extremely difficult to perform this adjustment rapidly and with adequate precision. To loosen one knob, at least one of the other two knobs must be tightened, and in most cases the actual adjustment direction that results from the tightening process is not the same as the desired adjustment direction. Furthermore, the assembly is relatively costly and decreases the stability of the system as a whole substantially; as a result, the camera images tend to oscillate particularly during and immediately following manipulation of the knobs, further hampering the adjustment process. The adjustments can also be easily lost if the knobs are inadvertently touched or are mistaken for the setting screw.
JP 2013-072996 describes a microscope system where a displacement and defocusing of an observation point can be corrected. To accomplish this, status information about states in which the focus adjustment and the rotational axis of the pivoting stand coincide is stored in a storage unit. These states can be specifically called up later. What is problematic in this case is that for every state that is not stored, costly calibration processes are necessary, and therefore deviations caused by a change in the pivot angle cannot be compensated for over the entire pivot angle range.
In general, calibration is costly because axial positions and axial alignments can vary between instruments due to manufacturing tolerances.
It is the object of the present disclosure to provide a digital microscope having a pivoting stand, and a method for calibrating the same. The digital microscope should be calibrated such that the system can be readily understood and easily handled even by inexperienced users, and such that a rapid generation of a focused image of a specimen detail, which is not displaced laterally in the image in relation to the vertical adjustment, is ensured for any pivot angle. This should be enabled even during automatic operation.
The digital microscope comprises, in a known manner, an optical unit, which comprises at least one objective and an image processing unit. A longitudinal axis of the objective forms an optical axis (Z-axis).
A pivoting stand has a pivot arm which is pivotable about a pivoting axis (Y-axis), and on which a support for holding the optical unit is arranged, preferably so as to be movable longitudinally by a motorized mechanism.
A specimen stage can preferably be adjusted by a motorized mechanism in at least two axes, which are ideally perpendicular to one another, with a specimen stage plane spanned by these axes being oriented parallel or nearly parallel to the pivoting axis (Y-axis).
The specimen stage and pivoting stand are preferably arranged on a base.
The digital microscope further has a control unit for controlling the optical unit, the pivoting stand and the specimen stage.
According to the present disclosure, the pivoting stand comprises an angle sensor for determining a current pivot angle of the pivot arm. The determined pivot angle is optionally used by the control unit to determine focus tracking and specimen stage tracking, enabling the focus and the specimen stage position to be corrected upon actuation of the pivot angle.
A method according to the present disclosure for calibrating a digital microscope having a pivoting stand comprises the following steps: adjusting a first pivot angle of the pivot arm; bringing a calibration marking located on the specimen stage into focus by moving the support along the optical axis (OA) or by moving the specimen stage in a vertical direction; centering the calibration marking with the optical axis by moving the specimen stage along two axes (X, Y) that are perpendicular to the optical axis (OA) when the pivot arm (07) is in the upright position; detecting and storing all first axial positions of the specimen stage and the support and of the first pivot angle; pivoting the pivot arm to a second pivot angle; bringing the calibration marking into focus for a second time; centering the calibration marking for a second time; detecting and storing all second axial positions of the specimen stage and the support and of the second pivot angle, determining a relative focus difference dF and a relative pivoting axis difference dx from the first and second axial positions; ascertaining a pivot-angle-dependent function for actuating a control unit of the digital microscope for the purpose of correcting the relative focus difference and the relative pivoting axis difference.
The differences determined during the calibration process are stored and are used for ascertaining an angle-dependent deviation of focus and centering position, which is then used during microscope operation for automatic focus tracking and image center tracking upon actuation of the pivot arm.
This calibration process is preferably performed in the factory, so that consumers receive a pre-calibrated instrument.
Additional calibration processes may optionally be performed by the consumer.
Some advantages of the present disclosure include particularly the fact that part of the cost-efficient calibration method can be performed at the factory, resulting in a substantial decrease over the prior art in the amount of adjustment and alignment that must be performed by the user. More particularly, the pivot angle of the pivot arm of a pivoting stand for digital microscopes can be infinitely varied without the viewed specimen detail changing in terms of image sharpness or its position displayed in the image. Object coordinates are advantageously indicated as relative coordinates which do not change with automatic focus tracking and image center tracking.
In this process, the position of the pivoting axis relative to the viewed specimen detail is assumed to be unknown. The specimen height that can be used for pivoting can be increased over the prior art.
The pivoting stand is also more stable and can be produced more cost-efficiently, since additional alignment points and/or a narrower tolerance range for all components that are relevant to the pivoting function can be dispensed with.
When the calibration method according to one embodiment of the present disclosure is used, users are required only to perform a set process, which is likewise simplified. This enables even users who are inexperienced with adjustment processes to operate the microscope, and dramatically reduces the amount of time required to achieve a deviation-minimized pivot function.
By additionally factoring in operating steps that must be performed in any case during the routine use of digital microscopes, the amount of time required from switching on the system to using a deviation-minimized pivot function can be decreased substantially over the prior art.
In principle, the specimen plane or the specimen detail being brought into focus does not have to lie at the height of the rotational axis actually in use. Therefore, in contrast to the prior art, the method is not limited to specimen heights which cannot be greater than the usable guide path of the lower Z-guide below the rotational axis actually in use. This even enables one of the two Z-guides, along with its control, to be optionally dispensed with as long as the movement ranges of the X-axis and the remaining Z-axis are large enough.
The cost savings that can be achieved over the prior art with the method according to one embodiment of the present disclosure and the simplifications of operation which produce faster results mean a significant optimization of the orientation of the product toward the targeted group.
In a preferred embodiment of the digital microscope, the angle sensor is implemented by means of two inertial sensors (acceleration or position sensors), one of which is arranged (with respect to the pivoting function) on a mounting plate in the stationary stand, and the other in the moved part (in the optical engine or in the zoom element). A vertical positioning of the pivot arm is characterized by a perceptible locking. In this locked position, the angle value of the inertial sensor of the moved part should be set, within the framework of a one-time calibration, to the angle value of the inertial sensor of the stand, so that for the locked position, a differential angle of 0° (ZERO) results. The pivot angle is thus determined from this differential angle. The advantage here is that these cost-efficient sensors can also be used with an inclined stand, with acceptable residual error.
Of course other types of angle sensors are also possible, with optoelectronic, magnetic and electrically operating angle sensors being suitable, for example.
The support and the specimen stage can preferably be moved by a motorized mechanism. Alternatively, the electric drive may also be dispensed with as long as a coding of the axial drives is provided. And this coding is necessary only in at least one axis provided for focusing and in the X-axis of the specimen stage, each of which is provided for the correction process (upper, lower or both Z-axes), in which case the adjustment to compensate for deviations can no longer be carried out automatically due to the lack of a motorized mechanism, and must instead be performed by the user based on the X- and Z-coordinates, which are then indicated as the target setpoints.
Transitioning to an indication of specimen coordinates is advantageous because deviations that result solely from the current environment of the system are not relevant to the user if they are automatically corrected by the system. Thus following a change in the pivot angle, not only are the position and sharpness of the specimen detail being focused on and visible in the image maintained, so are all indicated XYZ-coordinates.
If an upper and a lower coded or motorized Z-axis is present, a specimen height can also be read directly from this. For this purpose, the specimen plane is preferably positioned over the upper Z-guide at the height or Z-position of the rotational axis actually in use, with the coordinate display for the upper Z-guide showing a value of ZERO. The specimen height can then be read directly via the coordinate display for the lower Z-guide, and the user can be informed of this by a notation displayed accordingly with the coordinates.
The acquisition of data for focus tracking in the automatic correction process should preferably be carried out in a state in which the specimen plane is located near the pivoting axis, as in that case the deviations will be smaller, and correspondingly shorter movement distances will be required to compensate for the deviations, making this faster. Nevertheless, it is highly advantageous that the usable specimen height, which has heretofore been limited by the guide path of the lower Z-guide, can be increased for the pivoting movement according to one embodiment of the present disclosure, so that a pivoting movement is also supported for specimen heights that are greater than the guide path of the lower Z-guide.
In terms of a desired reduction in costs, due to the efficiency of the method according to one embodiment of the present disclosure, which can be realized even with greater deviations between the ideal pivoting axis and the pivoting axis, the pivoting stand can be equipped with only a single Z-guide, or the second Z-guide can be dispensed with.
In this case, the motorized X-axis of the motorized XY-stage and the remaining Z-guide would have to move greater distances for correction, however a significant reduction in overall costs would result, especially since the costs of electronics and of actuating the corresponding Z-axis can also be reduced as a result. In principle, it is also possible to eliminate the upper or the lower Z-guide. Using an upper Z-guide without a lower Z-guide results in a more stable assembly overall, and the specimen does not need to be moved vertically.
The specimen detail is preferably embodied as a cross. The arms of the cross in the X-direction are preferably long enough for any deviations that may occur in practical use.
The present disclosure is susceptible of various modifications and alternative forms, and some representative embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the inventive aspects are not limited to the particular forms illustrated in the drawings. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.